1. Field of the Invention
The present invention relates to video evaluation device, frame rate determination device, video process device, a video evaluation method, and a video evaluation program.
2. Related Background of the Invention
In a video process including acquisition, storing, transmission, displaying, encoding, decoding, etc. of a video, in general, the process is carried out on the basis of a fixed frame rate. Here, the frame rate is the number of frames processed per second. The fixed frame rate is the frame rate at which the number of frames processed per second is constant. As a concrete example of the fixed frame rate is defined as 29.97 fps (frame per second) according to, for example, National Television Standards Committee (NTSC) standards adopted in the United States and Japan. Alternatively, it is defined as 25 fps according to Phase Alternating Line (PAL) standards of National Television Standards Committee adopted in Europe. Further, the fixed frame rate of 15 fps or 24 fps may be used. A “video” is composed of successive “frame pictures”, which are individual still pictures.
When a video process is carried out at a fixed frame rate, if the frame rate is increased, the time intervals between successive frames become shorter. Due to this, it becomes possible to process a video smoother in movement. For example, a video to be processed at a frame rate of 30 fps has the number of frames per unit time larger than that of a video to be processed at a frame rate of 15 fps, therefore, the movement of the video is represented in a finer manner and a smoother movement is represented as a whole.
In addition to the video process at the above-mentioned fixed frame rate, a video process at a variable frame rate is also carried out. In the video process at a variable frame rate, the frame rate is varied in accordance with the amount of process of a video and the amount of data. For example, when a video is encoded, if it is judged that the amount of data to be encoded is large, the frame rate is reduced and the number of frames to be encoded per unit time is reduced. This is because if the amount of data increases, the time required for video process is increased. Here, at a variable frame rate, if the time interval between successive frame pictures is assumed to be T, the frame rate between two frame pictures is 1/T.
A technique to change such a frame rate is disclosed in, for example, Patent document 1 (Japanese Patent Application Laid-open No. Hei 11-112940).